San Francisco researchers have discovered that two chemicals commonly used in consumer products – bisphenol A and methylparaben – can interfere with the effectiveness of drugs used to fight breast cancer.
The research by doctors from California Pacific Medical Center in San Francisco is part of a growing body of evidence looking at the negative health effects of BPA, a plastic hardening chemical found in food containers, cans and even sales receipts, as well as methylparaben, a lesser-known preservative found in cosmetics and personal care products.
Scientific studies have linked the chemicals to hormonal problems and reproductive health issues, among other problems.
In the latest study, researchers took noncancerous breast cells from high-risk patients, grew them in a laboratory and found that once the cells were exposed to bisphenol A and methylparaben, they started behaving like cancer cells.
Tamoxifen, a drug designed to prevent or treat cancer, slows down the growth of both healthy and cancerous breast cells and ultimately leads to their death. But when tamoxifen was introduced in the lab, the cells exposed to the two chemicals kept growing and didn’t die, said Dr. William Goodson, senior clinical research scientist at California Pacific Medical Center Research Institute and lead author of the study.
The results are being published online this week in the medical journal Carcinogenesis.
Signal to consumers
Jeanne Rizzo, chief executive officer of the Breast Cancer Fund, a San Francisco advocacy group, said the study shows that BPA and methylparaben have a triggering effect when it comes to cancer. The next step, she said, has to be for consumers to demand changes that reduce environmental exposure to these chemicals.
A bill sitting on the governor’s desk would ban BPA in sippy cups and baby bottles manufactured or sold in California. AB1319 was authored by Assemblywoman Betsy Butler, D-Los Angeles. Similar legislation has failed in previous years.
The study looks at the fundamental mechanisms of how normal breast cells behave when exposed to BPA or methylparaben, said Dr. Mhel Kavanaugh-Lynch, director of the California Breast Cancer Research Program, which is administered by the University of California in Oakland and helped to fund the study.
Chemicals such as BPA and methylparaben mimic or interfere with the body’s endocrine or hormonal systems.
“We have a lot of information that makes these endocrine disruptors appear to be bad things to be exposed to, but there are very few, if any, studies that show a direct causal link,” Kavanaugh-Lynch said.
On a cellular level, Goodson and his colleagues focused on a gene – a critical pathway – that must be turned on for cancer cells to grow and work around the drugs designed to turn the cancer “off.”
The study found that healthy cells exposed to BPA and methylparaben started figuring out ways to bypass drugs like tamoxifen.
Drugs decrease estrogen
Since most breast cancers are driven by the hormone estrogen, the bulk of the drugs used to treat breast cancer are designed to knock down estrogen. BPA and methylparaben not only mimic estrogen’s ability to drive cancer, but appear to be even better than the natural hormone in bypassing the ability of drugs to treat it, Goodson said.
“There may be other routes of toxicity we’re just beginning to understand,” he said.
Scientists are increasingly looking at environmental causes for hormone-based cancers like breast cancer.
Breast cancer rates have been growing over the past 30 years. While some of the reason can be attributed to hormone-replacement therapies or other issues specific to women, researchers have noticed that breast cancer rates are going up by about the same amount in men as in women.
“It’s mostly a women’s disease, but when more men are getting more breast cancer, you have to wonder where the hormones are coming from,” Goodson said.
Goodson said BPA and methylparaben are hard to avoid because they are used so widely and are even found in household dust. He said he does not know whether the effects of exposure to the chemicals are reversible.
“It’s used so much. We kind of swim in it,” he said.
E-mail Victoria Colliver at firstname.lastname@example.org.
This article appeared on page A – 1 of the San Francisco Chronicle